Fine coal can be molded with the help of a external pressure in briquetting or extrusion installations or by agglomeration, e.g., pelletization. As a rule, one or more binders is added to the fine coal before the molding operation in order to impart adequate strength to these briquettes. Often molding must be followed by a thermal treatment and hardening with subsequent cooling of the briquettes, depending on the binder used.
The binders generally used, e.g., for anthracite briquettes, are substances that contain sulfur such as bitumen or sulfite waste liquor, but their sulfur content is unwanted for reasons of environmental protection. French Patent 861,930 describes sulfur-free binders of the type mentioned initially, e.g., a combination of powdered manioc (cassava) and molasses, but the resultant coal briquettes do not have adequate water resistance.
This invention is therefore based on a process to produce coal briquettes with a high water resistance despite the fact that they contain sulfur-free binders of the type mentioned above.